Project Summary In spite of decades of basic and clincial research, breast cancer remains the second leading cause of cancer death and the most commonly diagnosed cancer in American women . A major breakthrough for prevention and cure has been the appreciation that breast cancer is not one disease, rather a collection of cancer subtypes becoming better defined by improved methodologies based upon histopathologic, genetic and molecular signatures. Over time we have applied histological type, grade, tumor size, lymph-node involvement, and estrogen receptor (ER) and HER-2/neu receptor status to help define prognosis and probability of response to therapies, yet these alone have not fully captured the varied behavior of breast cancer. The field is now rapidly progressing with gene expression and proteomic signatures that will help personalize our interventions for individuals. This same concept is relevant to interventions for primary or secondary prevention and is the focus of our translational grant application. Our pre-clinical studies have demonstrated a strong benefit for dietary -3 fatty acid rich fish oil for the inhibition of ERPR(-)HER-2/neu(+) mammary tumors in a transgenic mouse model showing decreased tumor incidence, multiplicity and glandular atypia. Thus, our central hypothesis is that the development of aggressive breast cancer sub-types such as of ERPR(-)HER-2/neu(+) or ERPR(-)HER-2/neu(-) (i.e. triple negative) disease may be uniquely responsive to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the long chain -3 polyunsaturated fatty acids (PUFAs) found in fish oil. As a first step towards a future definitive prevention trial in women, we propose to test the efficacy of an -3 rich fish oil supplement to modulate breast biomarkers indicative of anti-carcinogenic action. We will randomize high risk survivors to a placebo-low dose or high dose -3 rich fish oil capsule treatment and employ our breast fine needle aspiration techniques to obtain cells and tissue for analysis of biomarkers of exposure and efficacy. Our multidisciplinary team has developed the following Specific Aims to: (1) Determine the effects of dietary -3 fatty acids on biomarkers of exposure and response in women at high risk for recurrent estrogen receptor, progesterone receptor breast cancer +/- HER-2/neu overexpression; and (2) Define the role of dietary -3 PUFAs in the epigenetic regulation of the inflammatory responses underlying mammary carcinogenesis as a novel mechanism for the effects of -3 PUFAs. Development of these biomarkers of -3 PUFA exposure and response will enable the assessment of this bioactive food component in future large-scale prevention trials for women at risk for recurrence of ERPR(-)HER-2/neu(+) or triple negative breast cancer.